1. Field of the Invention
This invention relates to a data transfer unit. More specifically, the invention relates to a data transfer unit which connects a data module to a plurality of host control units and which, when various commands are fed to the data module from the plurality of host control units, enables the data module to effectively receive these commands.
2. Description of the Related Art
In a cell phone employing the code division multiplex access (CDMA) system, it is an accepted practice to constitute a data transfer unit by connecting host control units constituted by a plurality of personal computers to a data module, and to feed various kinds of separate commands to the data module from the host control units, so that various data corresponding to the commands that are fed are processed in the data module.
FIG. 4 is a block diagram schematically illustrating a known data transfer unit in a state where two host control units are connected to a data module.
Referring to FIG. 4, the data transfer unit comprises a data module (DAT MOD) 41, a first host control unit (HC1) 42, and a second host control unit (HC2) 43. In this case, the data module 41 includes a first command module (COMOD 1) 44, a second command module (COMOD 2) 45, a first interface {I/F(1)} 46, a first on/off controllable interface {I/F(2)} 47, a second on/off controllable interface {I/F(3)} 48, a control unit (CPU) 49, a first connector 50, a second connector 51, and a third connector 52. Further, the first host control unit 42 includes a first connector 53 and a second connector 54, and the second host control unit 3 includes a connector 55.
The first command module 44, second command module 45, first interface 46, first on/off controllable interface 47, second on/off controllable interface 48, control unit 49, first connector 50, second connector 51, and third connector 52 are connected in the data module 41 in a manner as shown in FIG. 4. The first connector 50 and the first connector 53, the second connector 51 and the second connector 54, and the third connector 52 and the connector 55, are connected together through transfer lines (having no reference numerals), respectively.
The data transfer unit constituted as described above operates as described below.
The first host control unit 42 and the second host control unit 43 generate dedicated commands (request packet data), respectively, and the dedicated commands that are generated are fed to the data module 41. Here, the first host control unit 42 generates a relatively important dedicated command (hereinafter referred to as expedited command) of an indefinite period representing the switching operation or the change-over of transmission/reception, and the second host control unit 43 generates a general purpose dedicated command (hereinafter referred to as general purpose command) every predetermined period T0, i.e., every 500 msec. In the data module 41, the control unit 49 works to preferentially turn on the first on/off controllable interface 47 and to turn off the second on/off controllable interface 48 to monitor the arrival of the expedited command, so as to preferentially receive the expedited command fed from the first host control unit 42. When no expedited command has arrived but a general purpose command has arrived, the control unit 49 turns the second on/off controllable interface 48 on and turns the first on/off controllable interface 47 off.
FIG. 5 is a diagram of a waveform illustrating a state where a command is received by the data module 41 when an expedited command and a general purpose command are fed to the data module 41 in the data transfer unit illustrated in FIG. 4.
In FIG. 5, the abscissa represents the time and the ordinate represents the command waveform that is normally received by the data module 41. Here, black dots appearing on the time axis every predetermined period T0 represent a period for feeding a general purpose command, the upper side of the center line in the command waveform represents an expedited command waveform and the lower side of the center line represents a general purpose command waveform.
Referring to FIG. 5, the data module 41 that is fed with an expedited command from the first host control unit 42 during the period of from time t0 to time t1, permits the expedited command to be fed to the second command module 45 through the first on/off controllable interface 47 that has been turned on, whereby the second command module 45 processes the expedited command and transmits a response command (response packet data) to the first host control unit 42. During this period, the general purpose command is fed twice from the second host control unit 43. Here, however, since the second on/off controllable interface 48 has been turned off, the second command module 45 does not receive the general purpose commands and, hence, no response command is transmitted to the second host control unit 43.
Next, when the general purpose command is fed from the second host control unit 43 during the period of from time t2 to time t3, the data module 41 permits the general purpose command to be fed to the second command module 45 through the second on/off controllable interface 48 that has been turned on at the moment t2, whereby the second command module 45 processes the general purpose command and transmits a response command to the second host control unit 43.
Next, when the general purpose command is fed again from the first host control unit 42 during the period of from time t4 to time t5, the data module 41 permits the expedited command to be fed to the second command module 45 through the first on/off controllable interface 47 that has been turned on at the moment t4, whereby the second command module 45 processes the expedited command and transmits a response command to the first host control unit 42. During this period, the general purpose command is fed four times from the second, host control unit 43. Here, however, since the second on/off controllable interface 48 has been turned off, the second command module 45 does not receive the general purpose commands and, hence, no response command is transmitted to the second host control unit 43.
Then, when the general purpose command is fed from the second host control unit 43 during the period of from time t6 to time t7, the data module 41 permits the general purpose command to be fed to the second command module 45 through the second on/off controllable interface 48 that has been turned on at the moment t6, whereby the second command module 45 processes the general purpose command and transmits a response command to the second host control unit 43.
The above known data transfer unit preferentially receives the expedited command that is fed at an indefinite period from the first host control unit 42 and does not permit such an occurrence that the expedited command is not received, but frequently permits such an occurrence that the general purpose command is not received though it has been fed maintaining a predetermined period T0 from the second host control unit 43.
To avoid such an inconvenient state, means can be contrived according to which the time for monitoring the reception of the expedited command is set to be 10 seconds, and the reception is changed over to receiving the general purpose command when no expedited command is arriving even after the passage of 10 seconds. Even with this means, however, the general purpose command is not received for a period of 10 seconds of monitoring the reception of the expedited commands. The monitoring time of 10 seconds is considerably longer than the predetermined period T0 which is, for example, 500 msec of the general purpose command. Therefore, the state where the general purpose command is not received accounts for a considerable proportion of the time.
This invention was accomplished in view of the above technical background and provides a data transfer unit which reliably receives the expedited command when the expedited command has arrived, and changes over the reception to receiving general purpose commands when no expedited command is arriving.
For this purpose, this invention provides a data transfer unit comprising:
a data module having at least a command module, and first and second on/off controllable interfaces; and
first and second host control units; wherein
an expedited command output at an indefinite period from the first host control unit is fed to the command module through the first interface;
the first interface is turned off and the second interface is turned on at all times when a general purpose command output at a predetermined period from the second host control unit is fed to the command module through the second interface; and
the first interface is turned on and the second interface is turned off by an interface change-over signal of an active level fed to the data module just before the first host control unit produces the expedited command.
According to the above means, the first and second on/off controllable interfaces in the data module are so changed over that the first interface is turned off and the second interface is turned on at all times. It is therefore made possible to receive, during the change-over period, the general purpose command that is arriving at a predetermined period from the second host control unit as well as to set the interface change-over signal to assume the active level that is fed to the data module immediately before the expedited command arrives. Accordingly, the first interface is turned on and the second interface is turned off, and the expedited command from the first host control unit can be received just after the change over. Namely, the data module becomes capable of receiving and processing the expedited command without exception, and of successively receiving and processing general purpose commands in a period other than the period of receiving the expedited command. It is thus allowed to obtain a data module featuring a high command receiving efficiency.
It is further desired that the first host control unit in the above means works to set the interface change-over signal to the active level 10 msec before the expedited command is output.
According to this constitution, the change-over of the first and second interfaces has been completed based on the interface change-over signal of the active level that is fed at the time when the expedited command is fed to the data module and, hence, the expedited command can be reliably received and processed.
It is further desired that the first host control unit in the above means works to maintain the interface change-over signal at the active level while the expedited command is being output.
According to this constitution, the period of the active level of the interface change-over signal that is fed to the data module overlaps the period for feeding the expedited command. Therefore, means for changing over the first and second interfaces can be simply constituted and, besides, the change-over can be reliably accomplished to reliably receive and process the expedited command.